The present invention relates to a process and an apparatus for spatially enriching previously existing multi-channel material. More specifically, the present invention relates to a circuit including a number of components such as gain controllers, phase inverters and time delays which, in combination, modify Applicant's prior issued United States Patent (U.S. Pat. No. 5,056,149) for generating a multi-channel output from a single channel input. The present invention further relates to a process for generating a multi-channel output from a single channel input in accordance with the operations of the device.
Many contingencies exist wherein there is a need to increase spatial imagery in pre-existing stereophonic signals. Typical examples include synthetic music sources such as those created in the digital realm (e.g., digital synthesizers, samplers, etc.) and current standard recording techniques (e.g., placing microphones very close to an instrument or the performer's mouth in order to capture the music therefrom). In such examples, little spatial information, if any, is included in the original multi-channel recordings (or presentation technology). However, by using phase inverted paired signals ("PIPs"), which are two signals of equal frequency, content and amplitude but 180 degrees out of phase with one another, in conjunction with multi-channel sources, an increase in perceptual width, depth and sonic transparency will occur. In some instances, sound may appear to come from positions outside a "normal" stereophonic field as provided by two speaker "stereophonic" presentation.
Moreover, it bias become increasingly desirable to spatially position certain instruments, voices and the like so that their sonic images may appear in front or behind the rest of the output by such well known means as four channel surround sound matrix playback decoding equipment. In addition to "normal" left and right speakers, this matrix presents the summed signal (A+B) via a front-center speaker and the difference signal (A-B) via a rear-center speaker. Means are herein provided to control front to back imaging ratios.
Three embodiments of the present invention incorporate the concept of a "time mixer" to control spatial imaging. By controlling the arrival time of one channel of a multi-track source material with respect to all other channels, the Haas or precedence effect will make such "time modulated" channel to appear to be in front, with, or behind other multi-track channels. When incorporating such technology in conjunction with such as PIP circuitry and balance means, the "time mix" will result in producing dramatic sonic effects which may "project" the time modulated channel to virtually any sonic position desired.
Current technologies such as digital work stations and circuitry emulation systems, well known to those skilled in the art, provide electronic circuits by Digital Signal Processing ("CDSP") means. Though computer software modifications of such DSP programs, many sets of PIPs circuits analogous to the devices of FIGS. 1, 3 and 4 may be constructed. For example, in the DSP algorithm of FIG. 3, multiple PIPs may simultaneously lead, lag or be equal in time with a stereophonic synchronized time delay. The combination of multiple PIPs, in conjunction with balance controllers, such as a balance potentiometer which interfaces the modulated signal with the stereophonic signal field, provides the user with amazing capabilities for placement of a single instrument in a stereophonic or surround sound field. Due to the large number of PIP circuitry interrelationships made possible by such DSP programming means, many such contingencies cannot reasonably be illustrated herein, but should be considered within the scope of the present invention. However, each and every embodiment of the present invention may be employed in remastering pre-existing stereophonic and/or multi-channel sound.
With ever increasing frequency, multi-track studios are being replaced with digital two-track studios. Remixing two-track master recordings is currently considered impossible by many in the field. The apparatus of FIG. 1 is specifically designed to handle such a contingency situation. By summing or otherwise extracting portions of the input stereo signal and using the portions as a signal to a "M" input of the devices illustrated in FIGS. 2, 3 and 4, effective remixes from two-track sources are also made possible.
While it is anticipated that the major area of application for the present invention is to produce the sensation of three dimensional reality in a recording or remastering situation, many other uses are anticipated. In live sound reinforcement situations, lead instruments/voices may be sonically projected into the audience by such means as time modulation in conjunction with PIP technologies, whereby perception of "loudness" of the instruments/voices may occur without employing certain sound pressure levels toward the audience.
Post production film and video houses may have means for fully utilizing existing sound effect libraries or creating entirely new ones, with the creation of spatial relationships never found in nature. In current and future technologies, such as in digital broadcasting, codes utilizing spatial parameters as provided by the present invention may be separately from digital sound (e.g., music) information whereby a three dimensional matrix may be produced at the receiver with spatial information thereby achieved with extreme efficiencies.
As is now known to be the case of Applicant's prior issued United States Patent (U.S. Pat. No. 5,056,149), many new technologies such as CD-ROM, Digital Broadcasting and Virtual Reality applications will find much benefit in employing the present invention. While the present invention focuses upon reconfiguring stereophonic source material, it should be noted that FIGS. 1, 3 and 4, in the presence of monaural input signal, may be utilized in a manner similar, if not identical, to that of my above cited patent.
FIG. 1 of the present invention differs from FIG. 3 of my above cited U.S. Patent primarily in that it provides for stereophonic input with retention of input stereo information in the output. With monaural input, FIG. 1 would function virtually identically with the FIG. 3 of the prior cited patent. In some applications such as CD-ROM computer storage systems where storage space for audio information may be limited, use of such as FIG. 1 of the present invention (or the apparatuses of my prior cited invention), an effective stereo output may be produced by storing monaural audio data in conjunction with encoded data which may "drive" the apparatus wherein a second channel of audio information may thereby be produced. A similar area of application would be in broadcasting wherein due to bandwidth considerations, it may be advantageous to broadcast a monaural signal in conjunction with encoded data which may be decoded in the receiver to produce stereophonic sound. There are also advantages to this system inasmuch as no multi-path FM interference, commonly found in today's FM transmissions, would occur. Such applications would be evident in other areas, including digital broadcasting, to those skilled in the art.
In interactive virtual reality situations, such as either entertainment centers or commercial environmental (e.g. aircraft/spaceflight) similators, a monaural storage system could be controlled by varying algorithms of the present invention in FIG. 1 or the apparatuses of Applicant's prior cited patent whereby the user receives interactive audio feedback which corresponds with visual interactive stimulus information.
When employing stereophonic input to such virtual reality situations (the more common case), the stereophonic sonic environment can be manipulated in such interactive manner by all the apparatuses of the present invention.
In some virtual reality applications a third signal may be provided or generated in conjunction with a pre-existing stereo background signal. The apparatuses of FIGS. 3 and 4 would be especially effective in such situations inasmuch as a signal fed to the channel M input information could be made to appear in front, behind, or at any location within the pre-recorded stereophonic field. Therefore, modifications of the present invention with respect to four or more channel sonic fields would be obvious to those skilled in the art and thus, are not discussed herein.
In anticipation of interactive broadcasting, the present invention could allow monaural compatibility for non-participating viewers/listeners while providing the participant with means of total sonic interaction. Unique sonic contours may be produced by the present means whereby algorithms may be selected to optimize the sound for a given listening environment be it a home, a car, a studio, a dance club or a concert hall.
Whether in hardware or software form, many other areas of application not contained herein will be evident to those skilled in the art.